vacuum breaker under bathroom sink

[Daddy's truck]

I have a '05 Adventurer 38J which developed a leak under the bathroom sink (street side). There is a vacuum breaker under there, with 1/2" PEX tubing going into it via PVC connectors. The leak was by the connector that comes out the side of the brass vacuum breaker. Disconnected it all to see if the connector had a crack. Didn't see one under magnification. BTW, this connector is a 90 degree elbow with some type of check valve in it to prevent back flow. Put it all back together with teflon tape on the threads. Turned on the water going into the unit. At first, no leak. Waited about 30 minutes to check again - leak is back and worse than before. After researching this forum for similar threads, I'm more confused and have questions:
1. What the heck is this vacuum breaker for? Some threads claim it is part of the black tank setup, but it only leaks with the water system pressurized.
2. Can I get rid of the vacuum breaker and connect the 2 ends of the PEX together?
3. Does anyone know where I can buy a new 90 degree elbow connector-check valve-assembly? My local plumbing supply didn't have one and said to skip using the PVC elbow and connect the PEX directly to the vacuum breaker using a brass barbed 1/2 male threaded connector.
Help!!

[oemtech]

This vacuum break is a EPA required item from about 2004 and up and is part of the black tank flush system. I have had 2 of them go bad.

My fix is to take a 1/2" PVC 90 threaded elbow, 1/2" PVC treaded straight fitting and a short piece of 1/2 PVC pipe.



It's documented on my Free Tech Tips

[wagonmaster2]

oemtech - Thanks for the information. I've been reading about all the problems with the vacuum breakers but never knew what to look for or where to look on mine. Guess this is just one more problem we have to be aware of. It's difficult enough keeping up with all the maintenance required on these RVs (especially diesels) without having to keep replacing all the cheaply made products the manufacturers are using.
Thanks again for the picture.

Wagonmaster2
2004 Meridian 36G

[Daddy's truck]

Oemy:

Thanks for the reply. If you don't mind another question or two, what is the purpose of this assembly? Is it part of the black tank loop? The only thing that feeds the blank tank is the toilet. If not part of the black tank loop, why is it here?

Can it be removed permanently by using your pictured repair or was that a stop gap until the valve could be replaced?

[Hikerdogs]

Here's a link to an article explaining how a vacuum breaker (also known as a back flow preventer) works and what it's supposed to prevent.

http://www.dwbp-online.com/avb_flow.htm

Essentially it's used in a fresh water system to prevent water from being siphoned back into the supply system (either your fresh water tank or the municipal supply you're hooked to). They're used in every home newer than about 1980, and required on all outdoor faucets in our area.

Without it pollutants could be sucked into the fresh water supply if the supply pressure suddenly drops.

They are not unique to 2004 models and newer. Almost every Winnebago product I've seen uses one or more. We have one under the bathroom sink on our 01 Adventurer. I would definately advise replacing it rather than eliminating it. They are available at any home improvement store and most hardware stores. You can probably reuse the adaptors that go from the pipe fitting on the valve to the PEX tubing.

[hamguy]

You are receiving replies referencing 2 different devices. The one on the fresh water system is a backflow preventer and it keeps water from on source from entering another source and contaminating.

The other is a standpipe connected to drain systems to prevent the vacuum created when dumping from sucking the water from the P-Traps. That water is left in the traps to prevent orors from coming backwards to the inside of the coach.

The standpipe valve is a ball which opens to allow air input to replace the volume created by draining the tanks.

[Daddy's truck]

Hikerdog: Thanks for that link - it may have solved the mystery. When I re-installed the breaker, it IS on an angle - it is not plumb and the leak looks like it is coming from the top of the breaker rather than the fitting. I'll fix that and re-examine.

[oemtech]

This vacuum break is part of the black tank flushing system. The reason that it is usually located under the bathroom sink is that it must be 20" to 24" above the black tank flush nozzel to work correctly. This is according the the guy that makes them. I spoke with him at length while I was working on a customers rig. He showed me the process of how they were made.

[Hikerdogs]

The only reason it's part of the "black tank flushing system" is because it provides FRESH WATER to flush the tank. Any outlet hooked to the fresh water system is a potential source of contamination. If the pressure on the fresh water system goes to 0 or negative the contents of the black tank could be siphoned into the potable water system.

[AFChap]

Quote:

The only thing that feeds the blank tank is the toilet.

Not necessarily true. On MANY Winnebago coaches, the bathroom sink also goes to the black tank. I presume Winnebago does this to "help" us use plenty of liquid in the black tank, and I suppose it helps those folks who tend to fill the gray tank faster than the black tank.

[hamguy]

Quote:

Originally Posted by Hikerdogs The only reason it's part of the "black tank flushing system" is because it provides FRESH WATER to flush the tank. Any outlet hooked to the fresh water system is a potential source of contamination. If the pressure on the fresh water system goes to 0 or negative the contents of the black tank could be siphoned into the potable water system.

Ridiculous. There is no way the black tank could siphon back to the fresh water system. In order for a siphon to work is to have s continuous CLOSED path from one to the other. In a RV toilet, there is no such path.

[oemtech]

This is not an anti siphon valve! If is was it would release the water pressure and water left in the pipes when the flusher is turned off and dump the water under your sink. Just test your garden hose connection and you will see what I am talking about. Also the black tank would have to be about 99% full before it could siphon any water back thru the system because the sprayer is mount at the top of the tank.

[Hikerdogs]

Here's a link to the plumbing diagram for the fresh water inlet and supply on our 01 Adventurer.

http://www.winnebagoind.com/diagram/...v-fd_plumb.pdf


Page 7 sub section F shows the water inlets and fresh water piping to the bathroom. The vacuum breaker in the bathroom is hooked between the water supply to the black tank hose port and the flush heads inside the black tank. While the black water wouldn't contaminate the onboard fresh water supply (unless they were both teed to the same supply line) it certainly would be capable of contaminating the source supply if it were to be hooked up and the source supply failed.

Granted you would have to have a circumstance where the black water was above the flush jets, the flushing mechanism was attached to the water supply, the breaker valve failed (or was removed) and the supply pressure failed. While not a likely scenario the threat must be serious enough that code requires any outlet attached to a fresh water supply and a potential hazardous or toxic substance be protected by a vacuum breaker.

By definition a vacuum breaker is an anti siphon valve. Here's the first line of text in the article I linked explaining what a vacuum breaker is and how it works.

"The purpose of the atmospheric vacuum breaker is to prevent a siphon from allowing a contaminant or pollutant into the potable water system. This plumbing system safety valve is considered protection from high hazard or toxic substances, and may be used for low-hazard materials as well."

[oemtech]

Call it what you want... In my opinion it is a very poor design to have something like this under the bath room sink that allows water to flood your coach when it fails. A better design would have been to put the vacuum break/anti siphon valve in the water supply closet where the black flush hookup is. This way if it fails the water damage is at a minimum if any at all.

I got burn twice and then I eliminated it and added a standard anti siphon valve at the source.